This invention relates to a method for fabricating a semiconductor device, and more particularly to a method for forming a protection film by use of a chemical reaction in the case that the protection film is formed after the aluminium electrode is formed.
In a conventional method for fabricating a semiconductor device, whether a semiconductor device is a bipolar device, an MOS device or the like, it is necessary to form a protection film (e.g., made of phosphor glass, silicon nitride film) for protecting the semiconductor device from water, alkali metal or physical shock etc. after the aluminium electrodes are formed.
For example, in the case of fabricating ICs of a bipolar structure, a PSG (Phosphor-Silicate Glass) film is formed in approximately 3000 .ANG. thickness under a condition of normal pressure and thereafter, plasma Si--N film (silicon nitride film) is formed in approximately 5000 .ANG. thickness under the condition of reduced pressure. These PSG and plasma Si--N films function as protection films.
Such a conventional method for forming a protection film is carried out by use of CVD apparatus, a plasma apparatus etc. by controlling temperature and pressure. Therefore, the throughput of wafers largely depends upon the performance of the apparatus.
Further, as to a plasma Si.sub.3 N.sub.4 film, since its expansion rate is much higher than that of SiO.sub.2, stress migration occurs to Al electrodes and wiring so that the electrical performance of a semiconductor device is sometimes aggravated.